This invention relates to tufting machines and more particularly to a pattern attachment for a tufting machine for forming high pile and low pile tufts in the same row of stitching in accordance with a pattern determined by grooves or slots cut into a set of rotating slats.
In the production of tufted fabrics a plurality of spaced apart yarn carrying needles extend transversely across the tufting machine and are reciprocated cyclically to penetrate and insert loops of yarn into a backing material fed longitudinally through the machine. The loops are seized by respective loopers or hooks oscillating below the backing material in timed relationship with the needles as the loopers or hooks cross the needles just above the needle eye.
In loop pile machines the loopers point in the direction of feed of the backing material and hold the seized loops while the needles are retracted from the backing material. The loopers thereafter rock away from the point of loop seizure to release the loops. When the needles start their next descent the loops have been released from the loopers and carried one stitch length away from the needle path. In cut pile machines the hooks point in the direction opposite to the direction in which the backing material is fed so that the loops are fed onto the closed end of the hooks and each hook cooperates with a respective oscillating knife to cut the loops thereon in seriatim.
Although the pile height of cut pile fabric depends solely upon the distance that the hooks are disposed beneath the backing material, the pile height of loop pile fabric depends on the amount of yarn fed to the needles with the maximum being the distance from the loopers to the backing material. If the yarn fed to a particular needle is reduced, a low pile height loop will result. To control the supply of yarn, various methods have been devised in the prior art varying in complexity and versatility. Since a needle requires a certain amount of yarn so that it may shed a loop which is seized by a looper, when less yarn is fed than required by the needle, yarn will be pulled back or "back-robbed" from the prior stitch This is the basis for forming fabric with differing pile heights.
Wide use is made of yarn feed roller pattern attachments or assemblies for producing variations in pile height in tufted pile fabrics such as carpeting. These assemblies include a plurality of yarn feed rollers which feed yarn at different speeds to the needles of the tufting machine. Each of the feed rollers is selectively driven at one of a plurality of different speeds independently of the other feed rollers by means of clutches controlled by a pattern control. The amount of yarn supplied to the needles of the tufting machine is determined by the rotational speed of the feed rollers about which the yarn is wound, so that with a fixed needle stroke the amount of yarns supplied to each needle determines the pile height of the fabric produced. To create patterned pile effects the amount of yarn fed to the individual needle may be varied by driving the feed rollers selectively at the different speeds. When less yarn is fed than required by the needle, yarn is pulled back or back-robbed from the previous stitch which then becomes a lower loop. By feeding yarn at two or three speeds in a controlled manner, patterns may be formed by the different pile heights. Thus, high and low loops may be produced, or even three levels of loop when feed rollers of three different speeds are provided. Representative of such feed roller pattern attachments are those disclosed in U.S. Pat. Nos. 2,862,465 (Card); 2,875,714 ( Nix); 2,966,866 (Card); 3,001,388 (MacCaffary); 3,075,482 (Card); 3,103,187 (Hammel); 3,134,529 (Beasey); 3,272,163 (Erwin et al); 3,375,797 (Gaines); 3,489,326 (Singleton); 3,605,660 (Short); 3,752,094 (Short); 3,947,098 (Hammel); 3,926,132 (Lear et al); 3,955,514 (Prichard et al); 4,134,348 (Scott); 4,608,935 (Bardsley); and 5,182,997 (Bardsley).
Other types of pattern attachments may be used such as those having grooved or slotted slats as disclosed, for example, in U.S. Pat. Nos. 2,853,032 (Odenweller); 2,853,033 (Crawford); and 2,853,034 (Crawford). These pattern attachments comprise two sets of intermeshing slats mounted on a continuously moving roller chain. V-notches on one set are constant in height, but those on the other set, or pattern slats, vary in height according to the pattern requirements. As the two sets of slats intermesh, the length of yarn available for each tuft depends upon the extent to which the yarn is deflected by the depth of cut on the pattern slat.
The simplest of all prior art devices comprises a series of grooved cam disks which are eccentrically mounted on a drive shaft. A yarn strand is received within each respective groove in its path to a respective needle and as the disks rotate the tension of each yarn running in the groove changes and, as a result, differences in pile height are created. This method is limited to very simple loop pile patterns with very small repeats.
The desirability of providing a relatively simple pattern attachment that may produce random high and low, and also intermediate, loop pile fabric within a number of stitches substantially greater, i.e., a greater pattern repeat, than that produced by the cam disk pattern attachment is apparent. Presently, to provide such a pattern array involves utilization of one of the more complicated and costly aforesaid yarn feed roller attachments or intermeshing slat pattern attachments.